The present invention relates to polymeric compositions formed from a mixture of prescribed copolymers in certain defined ratios and the use of said composition to provide enhanced cement based building structures. The subject composition provides a water vapor barrier coating for cement based structures and an enhanced adhesion agent for materials applied thereto. Further, the composition, when applied to green (uncured) cement based structures, causes resultant cured structures to have enhanced strength and integrity.
Cement compositions and materials, such as concrete, cement block and the like, are common materials used in the construction industry. The term “concrete” and “cement” are each used herein and in the appended claims to refer to materials and structures formed of cement based compositions. The present invention is described by use of concrete building structures, such as slabs and the like, used as building flooring and wall structures although it is intended that other forms of cement based compositions be included in the present invention.
When concrete is poured, there is a period of time required to attain initial solidification of the concrete mixture. After initial setting, the concrete cures over an extended period of time during which hydration of the silicate and aluminate components develop and the excess water of the initial mix is lost. It is only after this extended period that the concrete has developed its full strength. In order for the concrete to properly cure and achieve its designed strength, the rate of water loss must be kept low. Such concrete is termed “green” structures while they are in their initial formation and in the partially cured state. Thus, it is well known that concrete structures contain and expel water for extended periods of time after initial formation.
When a concrete structure is formed directly adjacent to the ground or when grading of the surrounding terrain is complete, the structure in contact with ground material is continuously feed water from the ground by hydrostatic pressure. This is especially true when the concrete forms a grade-level or below grade-level flooring of a building or a below grade-level wall. In the case of a wall structure, the outside of the wall that is adjacent to the terrain is normally coated with a composition or structural forming membrane which inhibits the penetration of water into the wall material. Similarly, flooring slabs are normally poured over a bed of gravel and a plastic membrane to inhibit penetration of water into the slab formation. In both instances, the membranes are known to be less than completely effective due, in part, to imperfections in the membrane, imperfections generated during formation and pouring of the concrete, during backfill of the terrain against the wall structure, and from deterioration of the membrane over time. Thus, concrete structures have a tendency to take up water and expel the water through its free surface over extended periods of time.
When the concrete structure remains as formed and has an uncovered free surface, the water that escapes from the structure may be of a sufficiently small rate and in a form (e.g. water vapor) to be unnoticeable and inconsequential. However, when the concrete structure is intended to act as a substructure to be covered by additional material to form a finished structure, the additional material tends to trap the moisture. It has been previously suggested to coat concrete surfaces with various paints, including those based on an acrylate polymer in attempts to form water barrier coating. Such coatings generally exhibit poor adhesion and tend to spall from the concrete structure. These adverse effects cause deterioration of the applied finishing material as well as the bonding agent used to adhere finishing materials to the concrete substructure. Further, the trapped moisture may cause mold and other undesired formations to occur.
It is highly desired to be able to apply a sealer/coating composition capable of inhibiting moisture vapor emission from concrete structures, to have high adhesion to concrete structures and to enhance the adhesion of a concrete substructure to finishing materials commonly used in building industry. It is also highly desired to have a composition having the above properties that can be applied to green concrete substructures as well as fully cured concrete substructures to, thereby, enhance job scheduling and completion. It is further desirable to inhibit evaporation of water during initial curing of freshly formed concrete structures to allow hydration to occur slowly during curing and thereby produce a resultant structure having high strength and integrity.